JPH08156513A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE: To provide a general purpose pneumatic radial tire for passenger car having both satisfactory uniformity, and excellent cornering property and high-speed durability. CONSTITUTION: An inclined belt layer 6, a circumferential belt layer 7, and a tread 10 are successively arranged on the outer circumference of the crown part 4 of a carcass 3 extending over a pair of bead cores 2, the inclined belt layer 6 is formed of one or a plurality of strip bodies continuously arranged zigzag on the circumferential direction of a tire and bent parts arranged in positions of width directional end parts 9b, 9b, and the cord is formed of PET having a double twist structure. The twist coefficient N1 is 0.05-0.30, the tangential loss tanδ is less than 0.3 under conditions of initial tension 1kgf/piece, distortion amplitude 0.1%, frequency 20Hz, and atmospheric temperature 25 deg.C, the cord diameter is within a range less than 0.85mm. In the circumferential belt layer 7, the cord spirally wound and arranged substantially in parallel to the tire equatorial surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having good uniformity and excellent cornering property and high-speed durability, and more particularly to a general-purpose pneumatic tire for passenger cars.

[0002]

2. Description of the Related Art At the present time when energy saving is called for, in automobiles, studies are being made to improve fuel efficiency by reducing weight, and accordingly, tires are also being reduced in weight. The demand is increasing year by year, and this tendency is particularly remarkable in general-purpose pneumatic tires for passenger cars. Therefore, although attempts have been made to change the cords used for tires from steel cords to organic fiber cords, it is currently difficult to satisfy various tire performances.

Further, in the pneumatic tire, at least two inclined belt layers are laminated on the outer periphery of the crown portion of the carcass so that their steel cords cross each other.
It is common to have so-called cross belts.

However, the inclined belt layer is formed by cutting the cord rubber cloth into a predetermined width obliquely according to the arrangement angle of the cord. In this inclined belt layer, the cord cutting portion is the end portion. Inevitably occurs in. This is not desirable from the viewpoint of durability and the like, because separation tends to occur at the end portion of the belt layer.

In order to prevent the cord from being cut at the end portion of the inclined belt layer, a belt-shaped body having one or a plurality of cords covered with rubber is continuously arranged in a zigzag pattern in the circumferential direction. And by arranging the bent portion of the zigzag-arranged strip at the widthwise end position of the inclined belt layer,
It is useful to form an inclined belt layer, which is disclosed in Japanese Utility Model Publication No. 48-96259 and Japanese Unexamined Patent Publication No. 4-274904.
And Japanese Patent Laid-Open No. 5-319017.

[0006]

In the tires described in these publications, although the cord cutting portion does not occur at the end portion of the inclined belt layer, for example, as shown in FIG. 2, a linear step 11 ( (Shown by a thick line) inevitably occurs, and in addition, a zigzag step 12 may also occur depending on the winding method. The zigzag step 12 is generated by the arrangement in which the strips intersect and overlap with each other, and the cords are constrained to each other, which has the advantage of improving the shear rigidity of the belt. The step 11 in the shape of
There was no particular advantage, but rather the drawback was that it worsened the uniformity of the tire. This is a fatal drawback for radial tires for passenger cars, and it was necessary to develop means for reducing the linear step 11. From the viewpoint of weight reduction, it is desirable to use an organic fiber cord for the cord of the inclined belt layer,
No literature is found disclosing a clear technique for applying organic fiber cords to the cords of the inclined belt layer.

Therefore, an object of the present invention is to add polyethylene terephthalate (hereinafter referred to as "PE") to the cord of the inclined belt layer.
"T". ) Is used, the structure, the coefficient, the tangent loss, and the cord diameter of the organic fiber cord are optimized, and the difference in level of the inclined belt layer is substantially reduced to obtain good results. It is an object of the present invention to provide a pneumatic tire having both uniformity and excellent cornering property and high-speed durability, in particular, a general-purpose pneumatic tire for passenger cars.

[0008]

In order to achieve the above object, the present invention provides an inclined belt layer, a circumferential belt layer, on the outer circumference of a crown portion of a carcass that forms a toroidal shape across at least a pair of bead cores. And a pneumatic radial tire in which treads are sequentially arranged, the inclined belt layer is a belt-shaped body formed by coating one or more cords with a rubber, and the belts are continuously arranged in a zigzag shape in the tire circumferential direction, And,
It is formed by arranging the bent portions of the zigzag-arranged strips at the end positions in the width direction of the inclined belt layer, and the cord of the inclined belt layer is an organic fiber cord made of polyethylene terephthalate and has a twisted structure. Then, if the twist number of this code is T (number of times / 10 cm), the total denier is D _T , and the specific gravity is ρ, the formula: N _t = T × (0.139
× D _T / 2 × 1 / ρ) ^1/2 × 10 ⁻³ , the coefficient N _t is more in the range of 0.05 to 0.30, and the tangent loss is
tan δ is in the range of 0.3 or less under the conditions of initial tension of 1 kgf / piece, strain amplitude of 0.1%, frequency of 20 Hz, and ambient temperature of 25 ° C., and cord diameter is in the range of 0.85 mm or less. The circumferential belt layer is composed of at least one layer, is located on the inclined belt layer, and is formed by winding the cords in a spiral shape and arranging the cords substantially parallel to the equatorial plane of the tire. It is a radial tire containing.

Further, the width of the circumferential belt layer is narrower than that of the inclined belt layer, and the cord of the circumferential belt layer is
More preferably, it is an organic fiber cord made of PET or nylon.

Here, the twisted structure means one thread or two threads.
It means that more than one book is added and twist is added (from the bottom), and two or more pieces are drawn and multiplied by the opposite (from the top). The total denier D _T is the product of the yarn denier and the number of twists.

FIG. 1 shows a cross section in the width direction of a typical pneumatic tire according to the present invention. In the figure, 1 is a pneumatic tire, 2 is a bead core, 3 is a carcass, 4 is a carcass crown portion, and 5 is a tire. Circumferential direction, 6 is an inclined belt layer, 7
Is a circumferential belt layer, 8 is a belt-like member, 9 is a widthwise end of the inclined belt layer, and 10 is a tread portion. This pneumatic tire 1 is one in which an inclined belt layer 6, a circumferential belt layer 7, and a tread 10 are sequentially arranged on the outer circumference of a crown portion 4 of a carcass 3 that is in a toroidal shape and straddles at least a pair of bead cores 2. Is.

As shown in FIG. 2, the slanted belt layer 6 has a thickness of 1
A strip-shaped body 8 formed by coating a book or a plurality of cords with rubber,
It is formed by continuously arranging in a zigzag pattern in the tire circumferential direction 5 and arranging the bent portions 8a of the zigzag-arranged strips 8 at the width direction ends 9a and 9b of the inclined belt layer.
For example, as shown in FIG. 3 or FIG. 4, the inclined belt layer 6 includes a belt-shaped body 8 at a predetermined inclination angle from one widthwise end 9a or 9b toward the other widthwise end 9b or 9a. After winding, it is bent at this width direction end 9b or 9a (bending angle α), and then wound from the other width direction end 9b or 9a toward one width direction end 9a or 9b to be arranged in a zigzag shape. Then, this is repeatedly formed, and specifically, per N (integer) revolutions of the tire, a total of M (integer) bends are alternately performed at the width direction ends 9a and 9b, so that the tire is first wound. The inclined belt layer 6 is formed by determining the circumferential pitch for shifting the strip-shaped body to the front or rear such that the strip-shaped body and the strip-shaped body to be wound next are arranged at a predetermined interval. In FIG. 4, starting from the position 13,
The width direction end 9 of the inclined belt layer 6 during N times of tire rotation.
It shows a state in which the belt-shaped body has reached the adjacent position 14 of the starting point 13 after bending a total of M times at a and 9b. By this method, without creating a gap between adjacent strips,
It becomes possible to arrange the strips at an almost desired inclination angle. The inclined belt layer 6 obtained by this method has zigzag steps 12 as shown in FIG. That is, in the inclined belt layer 6 shown in FIG. 2, the cords are constrained to each other by the belt-shaped bodies 8 intersecting and overlapping each other. Therefore, as compared with the inclined belt layer shown in FIG. The rigidity can be improved.

The cord of the inclined belt layer 6 is made of PET.
It is an organic fiber cord made of and has a twisted structure. The twist coefficient N _t of the cord of the inclined belt layer 6 is 0.0
The range is 5 to 0.30. If it is less than 0.05, the code tends to come apart and workability tends to deteriorate,
Further, in order to secure the rigidity of the cord, it is necessary to set it to 0.30 or less.

Tangent loss tan δ of the cord of the inclined belt layer 6
Is an initial tension of 1 kgf / piece, strain amplitude 0.1%, frequency 2
Under the condition of 0 Hz and ambient temperature of 25 ° C., the range is 0.3 or less. The PET fiber cord has a large work loss and easily generates heat, so it easily generates heat and melts at high speed.
This is because there is a risk of finally causing a tire burst, and in order to prevent this, it is necessary to set the tangent loss to a range of 0.3 or less.

In order to reduce the linear step 11 of the inclined belt layer 6, the cord diameter of the inclined belt layer 6 is 0.85.
The range is less than or equal to mm. The number of layers of the inclined belt layer 6 is preferably a small number from the viewpoint of weight reduction, but can be increased as necessary, and the inclination angle of the cord of the inclined belt layer 6 is 15 ° with respect to the tire equatorial plane. In the range of up to 45 °, it is preferable to set the angle to 15 ° to 30 ° in consideration of easiness in production.

The circumferential belt layer 7 is composed of at least one layer, is located on the inclined belt layer 6, and the cords are spirally wound to be arranged substantially parallel to the tire equatorial plane. It is preferable that the width is narrower than the width. This is because when the widthwise end of the inclined belt layer 6 and the widthwise end of the circumferential belt layer 7 overlap at the same position, belt end separation tends to occur and high-speed durability deteriorates. Specifically, the end portion of the circumferential belt layer 7 is
It is positioned on the inner side in the tire width direction than the end of the inclined belt layer 6, preferably on the inner side in the tire width direction by 5 mm or more than the end of the inclined belt layer 6.

The number of the circumferential belt layers 7 is preferably about 1 to 2 from the viewpoint of weight reduction. Further, when it is necessary to effectively suppress the protrusion of the crown center portion during high-speed traveling, the circumferential belt layer preferably has two layers in the crown center portion and one layer in the remaining crown portion. When it is necessary to effectively suppress the belt edge separation, the circumferential belt layer 7 has a crown edge portion of 2 mm.
It is preferable that the layer and the remaining crown portion are made into one layer, which can be appropriately selected according to the application. The cord of the circumferential belt layer 7 is preferably an organic fiber cord made of PET or nylon in terms of weight reduction. Further, the tangent loss tan δ of the cord is preferably 0.3 or less for the same reason as the cord of the inclined belt layer.

The carcass 3 has a PET cord as its ply cord.
It is preferable to use an organic fiber cord such as the above, and to arrange the cord at an angle of 70 to 90 ° with respect to the equatorial plane of the tire.

[0019]

In the pneumatic tire of the present invention, the stepped circumferential belt layer 7 is placed on the tilted belt layer 6 and the diameter of the cord of the tilted belt layer 6 is reduced so that the tilted belt layer 6 is stepped. Can be most easily and substantially reduced, thus improving the uniformity of the tire.

Further, the widthwise end portions 9a of the inclined belt layer 6 are
Unlike the conventional sheet-shaped inclined belt layer, the cord is not cut at 9b, so that the separation at the belt end is reduced, and thus the high-speed durability is improved. Further, an organic fiber cord made of PET is used for the cord of the inclined belt layer 6, and in particular, by setting the coefficient of the organic fiber cord within an appropriate range, it is possible to reduce the weight of the tire and enhance the rigidity of the cord. Therefore, the cornering power is increased and the cornering property is improved.

In addition, by setting the tangent loss of the cord of the inclined belt layer 6 to be in the range of 0.3 or less under a predetermined condition,
This cord can be prevented from melting due to self-heating, and the width of the circumferential belt layer 7 can be set to the inclined belt layer 6
By making the width narrower than the width, the separation at the belt end can be prevented, and any of them greatly contributes to the improvement of high-speed durability.

[0022]

Next, specific examples of the pneumatic tire according to the present invention will be described with reference to the drawings. Example 1
The pneumatic tires used in Examples 1 to 5 have the cross section in the width direction shown in FIG. 1, and the tire size is 195 / 65R14,
An inclined belt layer 6, a circumferential belt layer 7, and a tread 10 are sequentially arranged on the outer circumference of a crown portion 4 of a carcass 3 having a toroidal shape that straddles between a pair of bead cores 2. The number of inclined belt layers 6, the cord material, the structure, the coefficient, the tangent loss, the cord angle, the cord diameter, the presence or absence of the circumferential belt layer 7, the cord material, and the structure are summarized in Table 1. It is shown. The inclined belt layer 6 is
It has the planar shape shown in FIG. 2, and according to what is shown in FIG. 4, M = 9 and N = 4, that is, the circumferential pitch f = 9 /
It was formed at a value close to 4. The circumferential belt layer 7 is
The cord is wound in a spiral and the tire equatorial plane is almost 0
The cords are arranged at an angle of °, the width of the circumferential belt layer 7 is 130 mm, and the inclined belt layer 6 (140 m
m) and the widthwise end of the circumferential belt layer 7 is made narrower than the widthwise ends 9a and 9b of the inclined belt layer 6.
Only 5 mm was placed inside the tire width direction.

[0023]

[Table 1]

The pneumatic tires used in Comparative Examples 1 and 2 did not have a circumferential belt layer, and the pneumatic tires used in Comparative Examples 3 to 7 had a cross section in the width direction shown in FIG. At least one of the coefficient, the tangent loss, and the cord diameter of the inclined belt layer is out of the appropriate range.

The pneumatic tire used in the conventional example is a two-layer pneumatic tire that extends at an angle of ± 22 ° with respect to the tire equatorial plane 5 and has a plurality of steel cords having a cord structure of 1 × 5 × 0.23. The inclined belt layers 6 are cross-laminated, and the circumferential belt layers 7 are not provided.

Test Method Each of the above-mentioned test tires was subjected to a test for evaluating uniformity, cornering property, and high-speed durability, and the tire weight was also measured. (1) Uniformity test A tire filled with a specified internal pressure is pressed on a drum with a specified load, the drum is rotated so that the tire rotates 60 times per minute, and the radial direction, lateral direction, and The unbalance amount of the force in the front-back direction was measured to evaluate the uniformity. Table 2 shows the test results.
The numerical values in the table are shown as an index ratio with the conventional example being 100, and the smaller the value, the better.

(2) Cornering test The cornering property was evaluated by determining the cornering power. For measuring cornering power, the outer diameter is 3
A test tire adjusted to an internal pressure of 1.7 kgf / cm ² was set on a drum of 000 mm, and a load specified by JATMA or JIS was applied to the tire from the above tire size and internal pressure. Preliminarily run at a speed of 30 minutes and the internal pressure is 1.7 kgf / cm ² with no load.
Readjustment, load the preliminary running load again, and set the slip angle to a maximum of 14 degrees (de) on the drum at the same speed.
g. ) Was continuously applied. The cornering force (CF) at each positive and negative angle is measured, and the formula: CP (kgf / deg.) = [CF (1 deg.) + CF (2 deg.) / 2
The cornering power (CP value) was calculated by + CF (3deg.) / 3 + CF (4deg.) / 4] / 4. Table 2 shows the test results. The CP value in the table is shown by an index ratio with the conventional example being 100, and the larger the CP value, the better.

(3) High-speed durability test The high-speed durability was measured according to the US standard FMVSS No. The test was performed by the step speed method according to the test method of 109, that is, the test was performed every 30 minutes at increasing speed until failure, and the speed (km / h) at the time of failure was measured and evaluated. Table 2 shows the test results. In addition,
The numerical values in the table are shown as an index ratio with the conventional example being 100, and the larger the value, the better. In addition, at this time, it is also investigated whether or not the code is melted, "Yes" if it is melted, "None" if it is not melted
Is described in Table 2.

[0029]

[Table 2]

From the test results of Table 2, Examples 1 to 5 are significantly lighter in weight than the conventional example, and in addition, uniformity, cornering property, and high-speed durability are all achieved in the conventional example. As good as

[0031]

According to the present invention, it is possible to provide a general-purpose pneumatic tire for passenger cars, which has good uniformity, excellent cornering property, and high-speed durability.

[Brief description of drawings]

FIG. 1 is a widthwise sectional view of a typical pneumatic tire according to the present invention.

FIG. 2 is a plan view showing a part of an inclined belt layer for showing a linear step 11.

FIG. 3 is a diagram illustrating a method for forming an inclined belt layer.

FIG. 4 is a diagram showing a method for forming an inclined belt layer.

[Explanation of symbols]

 1 Pneumatic tire 2 Bead core 3 Carcass 4 Carcass crown 5 Tire circumferential direction 6 Tilt belt layer 7 Circumferential belt layer 8 Band 9 Tilt belt layer width end 10 Tread 11 Linear step 12 Zigzag step 13 Start point 14 Adjacent position to start point 13 Code of inclined belt layer 6

Claims (4)

[Claims] 1. A pneumatic radial tire in which an inclined belt layer, a circumferential belt layer, and a tread are sequentially arranged on the outer circumference of a toroidal carcass crown portion that straddles at least a pair of bead cores. The inclined belt layer is formed by continuously arranging a band-shaped body formed by coating one or more cords with rubber in a zigzag shape in the tire circumferential direction, and bending the bent portion of the zigzag-arranged belt-shaped body into the inclined belt layer. The cord of the inclined belt layer is an organic fiber cord made of polyethylene terephthalate and has a twisted structure, and the cord of the cord has a twist number T (number of times / number of times). 10 cm), the total denier is D _T , and the specific gravity is ρ, the formula: N _t = T × (0.139 × D _T / 2 × 1 / ρ) ^1/2
The coefficient N _t represented by × 10 ⁻³ is 0.05 to 0.
The tangent loss tan δ is within the range of 30 and the initial tension is 1 kg.
f / line, strain amplitude 0.1%, frequency 20 Hz, ambient temperature 25 ° C., within a range of 0.3 or less, and
The cord diameter is in the range of 0.85 mm or less, the circumferential belt layer is composed of at least one layer, is located on the inclined belt layer, and the cord is spirally wound to be substantially parallel to the tire equatorial plane. A pneumatic radial tire characterized by being arranged. 2. The pneumatic radial tire according to claim 1, wherein the width of the circumferential belt layer is narrower than the width of the inclined belt layer. 3. The pneumatic radial tire according to claim 1, wherein the cord of the circumferential belt layer is an organic fiber cord made of polyethylene terephthalate. 4. The pneumatic radial tire according to claim 1, wherein the cord of the circumferential belt layer is an organic fiber cord made of nylon.